Among Abrahamic religions, we must make a distinction between Islam and the other two. Islam is born of a personal revelation to a single person and no witnesses. Judaism is born of personal but consistent revelations to several remarkable patriarchs and prophets, whom God used as instruments to perform great wonders and miracles, in the presence of the witness of an entire nation.
Finally, Christianity is born of the revelation of God Himself, who became incarnate in the human nature of Jesus Christ, to many thousands of the Jewish people, in whose presence He performed wonderful signs and miracles, culminating in His own bodily resurrection from the dead after being ignominiously executed on a roman cross.
In his resurrected body He appeared to many hundreds of His disciples, who went on to proclaim to the world the good news of His resurrection as a token of His promise of our own resurrection at the end of time. Many of them sealed their testimony on the resurrection of Jesus with their own blood, being cruelly persecuted by the Jewish authorities first, and put in jail, tortured and martyred by the romans several times afterwards, for three hundred years. Inexplicably, with each persecution the number of Christians grew quasi exponentially, until virtually the whole Roman Empire became Christian.
For Christianity (and I believe it is the same or very similar for the other two), God, in a way, contains the whole creation, and sustains all reality in being, because God is Being itself, and outside of Him there is nothing. Anything that is, is only because it participates in the being of God. But the universe is not divine, because, even if it exists within God and by God, its being is limited by the essences created in the mind of God, whereas God remains in the altogether transcendent realm of infinite (unlimited) being.
God is infinite being and, by logical necessity, cannot create something infinite, for something without limits cannot coexist on the same level of reality with something else, let alone something else also infinite. (For example, on the level of reality of the state of Texas, only one limitless property can exist). Therefore, creation is utterly dependent on God, but God remains entirely unchanged by it, for infinite being remains infinite even after sharing being with a multiplicity of beings.
And creation does not add anything whatsoever to God, because nothing can be added to something that is already infinite. The sum of God plus the created universe in no way can be greater than God alone, because nothing can be greater than infinite. (In fact, you cannot possibly add the universe to God, as if the universe was something foreign to Him; the universe is already within the divinity and only exists as a reflection of the divine being.) “In Him we live, we move and have our being.” (Acts 17:28)
Corollary: God is omnipresent to the whole creation, but remains transcendent to it, on a different status of being. When somebody asks, “is God real?”, I feel compelled to reply: “if your standard for what is real is your own existence, then the answer is no, because the reality of God cannot be put in the same category as ours.” If anything, you could say that, if we are real, then God is more than real. But not just one step above our level of reality, but an infinite number of levels.
To put it simply, our own reality vanishes in comparison with the reality of God.
Ignem veni mitere 